The purpose of this investigation is to evaluate whether exenatide, a type 2 diabetes medication, will improve the function of the innermost part of the arterial wall called the endothelium after a fat-enriched meal and to determine how this occurs. The results of this study will help to determine and understand a novel action of this group of diabetes medications based on the action of naturally occuring gut substances called incretins. This may have a significant impact on cardiovascular health in patients with early and longstanding diabetes.
Two independent, double-blinded, crossover substudies will be conducted to test the effect of exenatide on daylong post-meal and fasting endothelial function. We will measure endothelial function measured by peripheral arterial tonometry (EndoPAT2000, Itamar Inc.). Patients with recent onset (\<3 years) or established (\>5 years, Substudy 1 only) diabetes and impaired sugar tolerance (Substudy 2 only) will be studied. The plan is to complete studies in 75 patients (40 in Substudy 1 and 35 in Substudy 2). In Substudy 1 patients will get twice a day a skin injection of exenatide (Byetta) or identically looking placebo for 10 days, separated by 14-day period. On the next day after each treatemnt period (day 11), they get just one injection and eat a fat-enriched breakfast. A fatty lunch of similar caloric content will be given 4 hours following the breakfast. Endothelial function will be measured just prior to the injection and every 2 hours for total 8 hours. In Substudy 2, patients on 3 different days will get infusion of exenatide withg or without a blocking drug exendin-9, and a control test with placebo without exendin-9. Endothelial function will be measured before the infusion and 2 hours later during the final 15 minutes of the infusion cocktails. Patients will not eat any meal during the test visits.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
QUADRUPLE
Enrollment
Exenatide 5-10 ug sc BID/10 days
50 ng/min intravenously for 45 minutes on 2 out of 3 study visits separated by 5-10 days
Placebo sc BID/10days
Phoenix VA Medical Center
Phoenix, Arizona, United States
Reactive Hyperemia Index (RHI)
Greater RHI reflects greater endothelial function. It is calculated as average post-ischemia pulse magnitude divided by average pre-ischemia pulse magnitude. Results are expressed as least-square means of ANCOVA models.
Time frame: 0, 2, 4, 6 and 8 hours on Day 11 (Sub-study 1); 0 and 120 minutes on test Days 1, 2 & 3 (Sub-study 2)
Plasma Triglycerides
Triglycerides concentrations were measured before and 2, 4, 6 and 8 hours following study drug. Results are expressed as least-square means of ANCOVA models adjusted for sampling time and intervention sequence.
Time frame: 0, 2, 4, 6 and 8 hours post-study drug on day 11
Plasma Glucose
Plasma glucose was measured before and 2, 4, 6 and 8 hours following study drug administration. Results are expressed as least-square means of ANCOVA models adjusted for sampling time and intervention sequence.
Time frame: 0, 2, 4, 6, and 8 hours post-study drug on day 11
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Primed (6,000 pM/kg), continuous (600 pM/kg) intravenous infusion for 75 minutes on 1 out of 3 study visits.
Intravenous infusion for 45 minutes on 1 out of 3 visits